Hello,
I like the shots as well, my favorites being 2 and 3. They're awesome.
If I'd have to critique though, i agree with emp93 that the 1st would be richer with some more color.

Also I just learned this not long ago, you can actually reproduce quite nicely the polarizing filter effect if you have photoshop and i think the 1st photo could benefit from this.

I've learned it like so:
1. Create new transparent layer.
2. Apply a black to transparent gradient making sure black is on the top of the image.
3. Set the layer's blending option to "Soft Light" and you can then play with its opacity in order to control the strength of the effect.